Taiwanese Utility Patent No. M490043 discloses a projection apparatus for projecting plural images. The projection apparatus comprises an outer frame, an optical source module and a diffractive optical element. The optical source module is installed within a lateral end of the outer frame. The diffractive optical element is disposed within the outer frame and separated from the optical source module. The projection apparatus can project plural images. Consequently, the problem of projecting only a single virtual image by the conventional projection apparatus is overcome.
Although the conventional projection apparatus for projecting plural images is effective to overcome the problem of projecting the single monotonous image, there are still some drawbacks. For example, since the volume of this projection apparatus is large, the applications of the projection apparatus to modern wearable devices, portable communication devices, image capture devices and/or detecting devices are restricted. As a result, the optics or the associated optical components and even mechanical components, e.g., barrels or housings, may be too complicated.